i=1
sum=0
while i<=3:
    print('第',i,'个数')
    num=int(input())
    i=i+1
    if num<0:
        continue
    else:
        sum=sum+num
print('和为:%d'%sum)
"""i=11
while 10<i<20:
    square=i*i
    print(i,'的平方为：%d*%d=%d'%(i,i,square))
    i=i+1"""
